LEDs have found increasing usage due to their ability to conserve energy, and their longevity. The ability to control the dimming of LEDs in an efficient manner is thus desirable.
Thus, one objective of the present invention is a phase shift generation circuit which can adapt to variations in the number of phases needed for its output. By changing a digital number which is input to the system, the number of output phases generated can be varied, and the active outputs will maintain their even distribution over the period of the input pulse train. This feature permits the system to respond to external changes which result in changing the number of active LED channels, either as a result of user commands or other variations in the system performance. So for example, if it is detected that an LED output has failed, that output can be turned off, and the remaining LED output phases will redistribute evenly over the period of the pulse train period. This minimizes the amount of acoustic, electrical, and RF noise generated by the LED current pulses in a sensitive frequency range.
Another objective of this invention is a phase shift generation circuit that can automatically adapt to failures in the associated system, so that when channels in the associated system fail to operate correctly and are shut off, the remaining channels will operate with a uniform phase distribution. Output channels may fail for many reasons external to the integrated circuit used to realize the phase shift system, such as broken connections and open light emitting diodes. Control signals from the associated system will provide information about which channels are not functioning. In this case, a first logic block is used to count the number of operational channels, and a second logic block is used to assign the active pulse phase outputs of this invention to the active channels of the associated system. The counting block simply outputs a numerical code corresponding to the number of active channels, and this code is used as one input to the phase generation system. The assignment block receives information about which channels are disabled and assigns the active phase pulse outputs to the active channels to give a uniform pulse distribution.